In a cosmic twist of fate, two identical twins will follow each other into orbit next year during NASA's final planned shuttle mission to the International Space Station.
Scott Kelly and Mark Kelly of West Orange, N.J., are a pair of veteran NASA astronauts and captains in the U.S. Navy.
In October, Scott will launch aboard a Russian Soyuz spacecraft to begin a six-month tour of duty on the International Space Station. While he's there, his brother plans to visit aboard the last officially scheduled space shuttle mission, the STS-134 flight of Endeavour in February 2011. That mission is currently planned to be NASA's final shuttle mission before the orbiter fleet is retired. [ Photo of the astronaut twins ]
"We're looking forward to flying together," Mark Kelly told SPACE.com. "It's not expected. We're hopeful that this works out."
The twins, who were born six minutes apart in 1964 (with Mark arriving first), were chosen 32 years later to join the astronaut corps. The downside of having them in space simultaneously is that their parents will get a double dose of worrying.
"They certainly get nervous when we fly, but I think it's like all parents do," Scott said. "It's somewhat of a risky business, and we try to mitigate that risk as best we can."
The astronauts said they had been surprised and thrilled to both be chosen to join NASA.
"It's just a real privilege to be able to work for the space program," said Scott, a veteran of two space shuttle missions. "There's a lot of qualified people out there, and you know there's really a whole lot of luck and timing. We both feel very privileged to be able to serve our country in this capacity."
The brothers' missions are coming at a landmark time for the space program. Mark Kelly's shuttle flight will be the second of NASA's two final scheduled missions, though there is a chance one more will be added before the shuttles are retired. Discovery will fly to the space station in November, followed by the Endeavour crew next year.
"It will certainly be the last flight of Endeavour," said Mark, who has flown on three shuttle flights. "It's going to be sad to see the space shuttle retired, but you know, it's necessary."
NASA is retiring its three-shuttle fleet to make way for a new goal, to send astronauts to an asteroid by 2025.
The space agency has been flying space shuttles since 1981. Once they retire, NASA will rely on Russian, European and Japanese vehicles to fly cargo and crews to the space station until commercially built American vehicles are available.
For his part, Scott said he's excited to spend some quality time aboard the orbiting space station as commander of the Expedition 26 mission. He has visited the space station only once during his two spaceflights; the other flight was to the Hubble Space Telescope.
"I think its a great time to be flying on the space station, as the station gets complete and we can finally gear up our science program to a hundred percent," he said. "The space station is an amazing facility I think a lot of people dont realize just what an incredible achievement it's been."
Both brothers plan to share their experiences in space via the microblogging site Twitter. Scott Kelly posts Twitter updates under the name StationCDRKelly. Mark Kelly's Twitter posts appear under his pen name: ShuttleCDRKelly.